From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <shemminger@vyatta.com>
Subject: Re: Why is tcp_reno_min_cwnd() ssthresh/2?
Date: Fri, 4 Apr 2008 11:31:14 -0700
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Cc: "Xiaoliang David Wei" <davidwei79@gmail.com>,
	Netdev <netdev@vger.kernel.org>
To: "John Heffner" <johnwheffner@gmail.com>,
	"Lachlan Andrew" <lachlan.andrew@gmail.com>
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> Greetings all,
> 
> Apologies if this is a dumb question, but why does
> tcp_reno_min_cwnd()  return  ssthresh/2?
> 
> Since   ssthresh <- snd_cwnd/2   on loss, this looks like it tries to
> reduce  snd_cwnd  to 1/4 its value before a loss event, presumably
> then slow-starting back to half of the original  snd_cwnd.
> 
> As Tom Quetchenbach pointed out, it is also odd that  omitting
> min_cwnd()  from a congestion control module causes  ssthresh  to be
> used, giving different results from using  tcp_reno_min_cwnd().
> 
> Thanks,
> Lachlan

First sighed 5 years ago, and every times it comes up, the original
behaviour is retained.

http://oss.sgi.com/archives/netdev/2003-01/msg00114.html